Double-knot twine-knotters or twine-binders are predominantly deployed in large mobile rectangular bale presses for straw, hay, silage and similar materials, and also in the recycling of materials, e.g. for the bundling of paper, textiles, thin sheets, and similar.
Tying or bundling equipment fitted with such knotters can, however, also be components of packaging plants for the restraint of packs, bales, or bundles made up of suitable materials.
In large stationary or mobile bale presses the material to be baled is loaded into a bale press channel that is at least rectangular in cross-section, usually pre-compressed, and is pressed into a continuous rectangular body of material. The latter is divided into cube-shaped bales—also commonly designated as square bales—whose upper and lower faces, and also their outer faces in the longitudinal direction of the bale press channel, are strapped with a plurality of twine strands, which are knotted before the bale is ejected.
The supply of the necessary twine, the knotting process within the knotter and also the contribution of the bale press elements that take part in the formation of a double knot, are described in the document DE-27 59 976 C1 Hesston (also published as U.S. Pat. No. 4,074,623), which forms the starting point for the invention, and whose content contributes to the subject matter of the present disclosure, and which reference is incorporated herein by reference.
In the Rasspe company document “Twine-knotters for bale presses” recorded and distributed on a CD in 2002 at the time of the company's 175th anniversary, and whose content also contributes to the subject matter of the present disclosure, not only the general mode of operation of a twine-knotter, but also the differences between single and double-knotting, are presented in all their details.
Depending on the width of the bale and its density of compression, two or a plurality of double-knot twine-knotters are mounted next to one another on the knotter driveshaft of a bale press. The choice of knotters and bale press elements supporting the knotting process are determined by the number of turns required around the bale.
The knotter driveshaft is located either above or below the bale press channel, which is usually arranged horizontally, and as a rule is arranged parallel to the latter; in other bale press channels the driveshaft is arranged at the side.
The economic efficiency, e.g. of the recovery of straw feed, depends on the recovery, freight and storage costs. Straw, particularly in its chopped form, is used as litter in poultry barns, dairy cattle cubicles, and other types of stalls. It serves furthermore as a feedstuff in feed rations that are low in roughage, as a ground cover in strawberry cultivation, and as a culture medium for the growing of mushrooms. In order to enable such applications the large bale presses are fitted at the front with cutters or chopping devices. As a rule, pre-compression of the material takes place in a feeder channel that is mounted upstream of the main bale press channel; the material is only forwarded to the main bale press channel when a predefined quantity with a defined compression density is available. With such precautions highly compressed bales of high weight are generated.
Since the mobile bale presses are no longer just moved from one field to another, but are also deployed between farms, they must be suitable for travelling on roads, that is to say, they must satisfy the German Road Traffic Licensing Regulations. From this it follows that the dimensions of the machinery cannot be increased in an unlimited manner. Also the dimensions of the individual bales must be suitable for optimal loading onto trucks and subsequent storage.
In order to increase the weight of the bale even further, as a result of which the available transport capacity can be utilised better than before, and the content of a bale is increased, an increase of the compression of a bale is sought whilst maintaining a comparable level of moisture in the material. With such an objective, however, it must be borne in mind that the plastic twines that are available at the present time are predominantly polypropylene twines that have a limited tear resistance; with an increased density of the compressed material they would tear when the bales are ejected out of the bale press channel. The thickness of the baling twine, which is determined in terms of the length of the twine strand, expressed as how many metres of twine weigh one kilogram (unit: m/kg), cannot be increased without further measures being taken, on the one hand because the individual knotter components are designed to process the baling twines that are on the market, while on the other hand, thicker twines with increased tear resistance would disadvantageously increase the dimensions of the double-knotter, wherein it is uncertain whether reliable functioning of the knotter in accordance with the so-called Deering operating principle could be achieved at all. With increasing twine thickness the knot strength represents a further problem.
In order to avoid failures, therefore, the force required to hold a bale together must be distributed over more twine strands than have previously been achievable. If the distance between the individual twine strands is less than previously prescribed by the width of the twine double-knotter, this also has an advantageous effect on the cohesion of a bale consisting of finely chopped straw.
In order to increase the weight of a straw bale—assuming the same dimensions and the same moisture level—e.g. by 25%, a large bale press of the generic kind, which was previously fitted with 6 double-knot twine-knotters in accordance with Hesston, would have to be equipped with 8 knotters, but with the length of the knotter driveshaft unaltered. The double-knot twine-knotter of the generic kind described in the document DE-27 59 976 C1 (Hesston) consists of a drive device, in what follows also denoted as a “drive module”, a frame, in what follows also denoted as a “knotter chassis”, and also a knotter module and a blade lever, and requires sufficient distance from the adjacent double-knot twine-knotter such that the drive arm of the blade lever, articulated on the frame, whose lower end opens out into a bifurcation, does not impact on the adjacent double-knot twine-knotter, if it moves into its outer deadpoint position.